1. Field of the Invention.
The present invention relates to cutting tools of the type utilizing diamond cutting elements and to an improved cutting element with a complementary profile which allows a closer spacing of like cutter elements than previously possible.
2. Description of the Prior Art.
A variety of cutting tools are known which are well suited for receiving diamond cutting elements as the cutting or wear portion of the tool. Such tools are found, for instance, in the mining, construction, and oil and gas exploration and production industries and include earth boring bits, under reamer hole openers, and the like. Commercially available earth boring bits can be generally divided into the rolling cutter bits, having either steel teeth or tungsten carbide inserts, and diamond bits, which utilize either natural diamonds or artificial or man-made diamonds. The artificial diamonds are "polycrystalline", used either individually or as a component of a composite compact or insert on a cemented tungsten carbide substrate. More recently, artificial polycrystalline diamonds have been developed which are stable at higher temperatures than the previously known polycrystalline diamond. Both types of polycrystalline diamond are available in a variety of shapes and sizes.
The diamond earth boring bits can be generally classified as either steel bodied bits or matrix bits. The steel bodied bits are machined from a steel block and typically have cutting elements which are press-fit into openings provided in the bit face. The matrix bit is formed by coating a hollow tubular steel mandrel in a casting mold with metal bonded hard material, such as tungsten carbide. The casting mold is of a configuration which will give a bit of the desired form. The cutting elements are typically either polycrystalline diamond compact cutters braised within an opening provided in the matrix backing or are thermally stable polycrystalline diamond cutters which are cast within recesses provided in the matrix backing.
Cutters are often placed in a straight row extending from a central location on the bit face out to the full bit diameter. Alternatively, cutting elements are set in individual mountings placed strategically around the bit face. With either arrangement, more than one cutting element is typically placed side-by-side on the bit face with the cutting faces of the cutting elements being located in a radial plane from the axis of rotation of the bit. The cutting elements themselves, whether stud mounted or placed within openings in the matrix material have generally been manufactured with circular cutting faces. Because two circular cutting faces places side-by-side in a cutting plane fail to achieve full coverage of that plane, it was generally necessary in the past to provide a staggered cutting arrangement on the bit face with alternate cutter rows achieving full coverage.
Although polycrystalline diamond cutting elements are commercially available as segments of circles, these alternate cutting shapes have not been utilized, to my knowledge, to achieve increased density and hence full coverage of a cutting plane on a diamond bit face. Square cut polycrystalline diamond cutting elements are also known but do not include mating recesses to provide a complementary profile on the bit face to achieve full coverage of a cutting plane with a single blade of cutting elements arranged side-by-side.
The present invention has as its object to provide a polycrystalline diamond cutting element having a mating recess which allows a complementary fit with an adjacent cutter to achieve full coverage of a cutting plane.
Another object of the invention is to provide a method of manufacturing a cutting tool which allows worn diamond cutters to be salvaged and utilized without detracting from the performance characteristics of the cutting tool.
Another object of the invention is to provide a polycrystalline diamond bit with an increased density of cutting elements in a single bit blade.
Another object of the invention is to provide a method for manufacturing polycrystalline diamond cutting elements more economically by cutting a plurality of cutting elements from a single blank, the elements sharing a common boundary.
Additional objects, features and advantages will be apparent in the written description which follows.